The combustion of wood in a fireplace or stove results in the pyrolysis of a significant fraction of the wood thereby producing wood tars and soot which are carried about the fireplace and up the flue by the rapidly rising hot combustion gases. Wood tar includes both liquid and solid components, the tar often further being distilled by the heat to form creosote, wood pitch and, of course, soot. Because the walls of the firebox and the flue are comparatively cool, particularly when the fire has been burning for a relatively short time, the vaporized tars condense on the surfaces of the firebox and flue. A sticky deposit is formed to which soot particles readily adhere and the build-up of such deposits provides the opportunity for dangerous flue fires.
The use of catalysts to promote combusion of organic substances, including elemental carbon, below their autoignition temperatures is known. U.S. Pat. No. 3,684,576 to Eisen et al discloses use of various catalysts including platinum and cobalt acetal acetonate disposed on top of a substance to remove such substance from a metal substrate at a temperature somewhat below 400 degrees centigrade, 350 degrees centigrade being described as a practical lower limit. U.S. Pat. No. 3,598,650 to Lee discloses the inclusion of a metal oxide, preferably cobalt, in the vitreous porcelain enamel lining of an area to effect self-cleaning action at temperatures above 350 degrees centigrade. U.S. Pat. No. 3,800,466 to Heit addresses the problem of the black liquor by-product of paper-making processes and the slag resulting from the combustion of the aqueous alkaline fuel (black liquor) in recovery boilers. Heit discloses the use of water-soluble salts of a catalyst metal selected from the group consisting of manganese, copper, iron, tin, nickel, cobalt and mixtures thereof. A sequestering agent is added to the alkaline pH aqueous solution of the catalyst metals and the resulting mixture is mixed with the aqueous fuel (black liquor) just prior to its injection into the combustion zone of the recovery boiler.